The overall aim of this project involves the use of nuclear magnetic resonance (NMR) spectroscopy to characterize biological macromolecules and their interaction with compounds of environmental concern. During the past year, we have been involved in collaborative studies with Dr. Linda Luck at Clarkson University, on bacterial periplasmic receptor proteins. These proteins provide a extremely attractive model systems for studying the general problem of receptor-ligand interactions, since they are relatively small and highly soluble. Initial studies on the glucose/galactose receptor (GGR) have involved the structural and dynamic changes which accompany glucose complexation. Order parameters for the five fluoro-tryptophan residues in the receptor were determined based on relaxation data; Residues 183, 127, 133, and 195 exhibited a mean order parameter S2 = 0.89, while residue 284, located in the hinge region of the receptor, has an order parameter of 0.77. Changes in the 19F relaxation rates upon glucose complexation are consistent with a more compact structure which has a shorter molecular correlation time. More recent studies on isotopically labeled complexes have revealed shift perturbations due to dynamic frequency shift effects. These perturbations are dependent on the details of molecular dynamics, and are currently being analyzed. Future work will involve studies with structural analogs, in an effort to determine how broad the receptor specificity is, and to determine the molecular basis for the observed specificity. In parallel with these studies, we have continued our theoretical investigations of dynamic frequency shifts, and have extended the treatment to include coupled spin systems involving nuclei of arbitrary spin. The formation of protein adducts by environmental agents involves complex chemical/biochemical/structural interactions which are, at best, incompletely understood. We have recently been developing methods for the assignment of these adduct resonances, and the interpretation of the structural perturbations which they introduce. NMR studies of reductively methylated (by formaldehyde) and carboxymethylated (by bromoacetate) ubiquitin are currently in progress. The NMR technique is uniquely suited to the characterization of the heterogeneous adducts which can form under typical physiological conditions. One unexpected result of these studies is that highly carboxymethylated proteins such as ubiquitin appear to exhibit significant structural alterations, perhaps due to partial, but not complete, denaturation.